In a few minutes, as Hollywood writers consider a strike, one writer imagines a conversation with economist Adam Smith.

COHEN: But first, the Iraqi government approved draft legislation today that would lift immunity for private security companies like Blackwater. This comes after news that the U.S. State Department has promised limited immunity to bodyguards from Blackwater - that immunity in exchange for information about the shootings last month that left 17 Iraqis dead.

From more on how immunity might affect the case, we're joined now by NPR justice correspondent Ari Shapiro. Hi, Ari.

ARI SHAPIRO: Hey, Alex.

COHEN: So the Blackwater guards were granted, quote, unquote, "limited use immunity" by the State Department. What exactly does that mean?

SHAPIRO: Yeah, well, specifically they were told that the statements they made and the fruits of the statements they made could not be used against them in any prosecution. So what that means is they're not immune from a prosecution, but if somebody was being interviewed and they said, yeah, I was sitting here and I saw so and so shoot somebody, not only can the investigators not use that statement - that so and so shot somebody - but if they then go and interview the person who was identified in the statement, those are the fruits of the statement that also cannot be used against the prosecutors. So you've got this whole circle of information, this realm of really valuable information that the Justice...

COHEN: But you can't use any of it. It seems like...

SHAPIRO: Right, exactly. And so you had a whole team of investigators whose investigation was basically tainted because the State Department offered this immunity without checking with the Justice Department, without checking with the FBI, without checking with the people who are going to be carrying out the investigation in the eventual prosecution.

COHEN: Now, if you couldn't necessarily use any of this information because of this limited immunity, why would you go after it? Why would you offer immunity in the first place?

SHAPIRO: That's what the Justice Department and FBI folks must be asking themselves right now. You know, the State Department was the one that offered this immunity and they aren't the ones who do the investigation on the prosecution, so obviously you have different interest that play here. The State Department may want one thing while the FBI and the Justice Department just want to bring people to justice. They want to carry out these investigations and prosecutions, and so there seems to be a lot of frustration and tension there that the State Department did this without checking with anybody first.

COHEN: Now, there were already some questions about the challenges of this case given that the people in question were private contractors, they were not U.S. military, this happened on foreign soil, so how might this latest twists regarding immunity affect the situation?

SHAPIRO: Right. This is a perfect storm of legal issues, and the question is whether these contractors are in just a legal black hole or whether there is any way to hold them accountable for actions that took place when they weren't in the Green Zone, whey they were in Iraq. They're, as you said, not members of the military. So there are all of these legal worlds that the Blackwater guards were outside of. And the question is, what legal world could they be inside of? The Iraqi legislature is, as you mentioned, looking at legislation that would hold them accountable, Congress here in the United States is looking at legislation that would hold them accountable, but right now, there's really no clear answer to this question of where they could be tried, prosecuted, and held to account for their actions.

COHEN: Ari, the FBI is now re-interviewing Blackwater employees and they aren't offering any sort of immunity, how might the information that they gather be used?

SHAPIRO: Well, the goal is to construct some kind of a prosecution that can hold up in court despite the limited immunity that the State Department folks offered these guards early on. It's going to be really hard. Any defense lawyer is undoubtedly going to try to argue that, somehow, this investigation or prosecution was tainted by the statements or the fruits of the statements that shouldn't come into play. So the FBI has a very, very high bar that they have to reach now to try to piece something together that could stand up in a criminal court.

COHEN: Let's talk for a moment about physical evidence. The evidence in the September 16th shooting was gathered by Iraqi authorities and, of course, many of the witnesses live in Iraq. What would need to happen to use any of that to legally pursue this matter here in the United States?

SHAPIRO: You may remember when we talk about enemy combatant issues - arresting people on the battlefield or detaining people on the battlefield who may be terrorists, there's been all this conversation about the challenges of maintaining the integrity of evidence on the battlefield. Well, if we want to try the Blackwater guards in criminal court, you run into those same challenges. How do you maintain the evidence? How do you get these witnesses, these civilians from Iraq, how do you bring them to the U.S., put them in a court, and get them on the witness stand? It's a huge challenge independent of these issues of immunity that we've been talking about.

NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.